Hard magnetic properties of melt-spun Mn-AI-C alloys

摘要

Structural and magnetic characterization of Mn_(x-y)Al_(100-x-y)C_(2y) (x = {50, 55}; y = {0, 1}) melt-spun ribbons is reported. To obtain the metastable ferromagnetic τ-phase, rapidly solidified alloys were annealed either in a vacuum furnace at 823 K or directly in the vibrating sample magnetometer under applied magnetic field. Optimal magnetic properties were demonstrated by Mn_(54)Al_(44)C_2 samples proved to be single-phase with a coercivity of 0.19 T measured in both cases. For this composition the structural ε→τ phase transformation has been magnetically detected at 786 K, Curie temperature of τ-phase (T_c = 592 K, T_p = 610 K) has been determined using mean field approximations in ferromagnetic and paramagnetic regions. Rietveld refinement of X-ray diffraction spectra was employed to analyse the phase constitution of annealed alloys, lattice parameters as a function of chemical composition and mean grain size for the phases involved.